1. Field of the Invention
The present invention generally relates to an organic electroluminescent (to be abbreviated as xe2x80x9cELxe2x80x9d hereinafter) device, more particularly, to an organic EL device with efficient heat dissipation employing an additional heat dissipation layer and a method for manufacturing.
2. Description of the Prior Art
The organic EL device has attracted tremendous attention due to its advantages over other display panels. These advantages include larger visual angle, shorter response time, smaller dimension in thickness, lower power consumption, simpler fabrication, no need for backlighting, and the ability for light emitting in a full color range.
Please refer to FIG. 1, which is a cross-sectional view showing the structure of a conventional organic EL device in accordance with the prior art. The organic EL device is characterized in that at least a first electrode 12 is formed on a substrate 11, furthermore, there are an organic layer 13 with at least an organic emitting layer, and a second electrode 14 formed by sequential evaporation in cross touch way on the first electrode 12. Then, a sealing cap layer 15 formed of resin is employed to protect the organic layer 13 from the external oxygen or the moisture.
Since, in an organic EL device, the light is generated when the electrons and holes from the first electrode 12 and second electrode 14 combine in the organic layer 13 to excite the organic emitting layer, it is inevitable that heat is generated during the luminescence process. Once the heat encounters the moisture existing inside the sealing cap layer 15, dark spots due to oxidation will be formed on the surface of the organic layer 13. The existence of such dark spots adversely affects the luminescence quality such as luminescence intensity and luminescence uniformity of an organic EL device. According to the so-called xe2x80x9c10-degree rulexe2x80x9d, the lifetime of the device reduces to half for every 10-degree rise in operation temperature. Therefore, for a highly heat-generating device, the performance as well as the lifetime depends strongly on the ability in heat dissipation. More seriously, the lifetime of an organic EL device may be substantially shortened.
In order to overcome the image defects and shortened lifetime due to the disability in heat dissipation, the industry has developed a number of prior art organic EL displays, for example, in U.S. Pat. No. 5,948,552 xe2x80x9cHeat-resistant organic electroluminescent devicexe2x80x9d filed by Antoniadis, et al. and U.S. Pat. No. 4,895,734 xe2x80x9cProcess for forming insulating film used in thin film electroluminescent devicexe2x80x9d filed by Yoshida, et al. However, in the aforementioned prior arts, additional materials are required with little concerns in structural reform. Little improvement in device performance is disclosed for organic EL devices.
Therefore, there is need in providing an organic EL device with efficient heat dissipation employing an additional heat dissipation layer and a method for manufacturing such a device so as to prolong the lifetime and improve the reliability.
Therefore, it is the primary object of the present invention to provide an organic EL device and a method for manufacturing such a device, characterized in that a heat dissipation layer is interposed between the first electrode and the organic layer and that a plurality of contact windows are provided in the heat dissipation layer so as to connect the organic layer and the first electrode, such that the heat generated in the organic layer during operation dissipates out of the active region of the device and thus the device lifetime is prolonged and the reliability is enhanced.
It is another object of the present invention to provide an organic EL device and a method for manufacturing such a device, characterized in that structural reform of the heat dissipation layer and the contact windows facilitates the development of the organic EL device.
It is still another object of the present invention to provide an organic EL device and a method for manufacturing such a device, characterized in that structural reform with a few more processing steps not only overcomes the problems related to the disability in heat dissipation but also reduces the manufacturing cost.
It is still another object of the present invention to provide an organic EL device and a method for manufacturing such a device, characterized in that the heat dissipation layer has good electric conductance such that the voltage drop across the first electrode and the organic layer is significantly reduced.
In order to achieve the foregoing objects, the present invention provides an organic EL device, comprising: a substrate; at least a first electrode formed on the substrate; at least a heat dissipation layer formed on the first electrode, wherein the heat dissipation layer comprises a plurality of contact windows exposing portions of the first electrode; at least an organic layer formed to cross the heat dissipation layer partially, covering the exposed portions of the contact windows to contact the first electrode; and at least a second electrode formed on the organic layer.
The present invention further provides a method for manufacturing an organic EL device, comprising steps of:
a. forming at least a first electrode and a heat dissipation layer in turn on a substrate;
b. forming a plurality of contact windows by etching portions of the heat dissipation layer so as to expose portions of the first electrode corresponding to the portions of the heat dissipation layer;
c. forming at least an organic layer to cross the heat dissipation layer partially, so as to cover the contact windows and contact the first electrode; and
d. forming at least a second electrode by vertical evaporation on the organic layer.
Other and further features, advantages and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings are incorporated in and constitute a part of this application and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.